Minecraft on Mac OS X uses the older, Apple supplied Java 6 even when the newer Java 8 supplied by Oracle is installed. If this cannot be worked around because of Apple's restrictions I understand but if it's possible to change that would be great because Javas 7 and 8 perform MUCH better than Java 6. If this belongs in the Minecraft Launcer section, I apologize.
It is possible to change which Java Minecraft uses in the launcher, but you first need to know the path to the JRE 7 / 8 javaw.exe program. Find that and then input it into the 'Executable:' option in the launcher profile settings.
Edit: If you do not know the path to your Java executable, the default is C:\Program Files\Java\jre7\bin\javaw.exe for Java 7 and C:\Program Files\Java\jre1.8.0_20\bin\javaw.exe for Java 8.